Clover

Clover, also called trefoil, are plants of the genus Trifolium (from Latin tres 'three' + folium 'leaf'), consisting of about 300 species of flowering plants in the legume family Fabaceae originating in Europe. The genus has a cosmopolitan distribution with highest diversity in the temperate Northern Hemisphere, but many species also occur in South America and Africa, including at high altitudes on mountains in the tropics. They are small annual, biennial, or short-lived perennial herbaceous plants, typically growing up to tall. The leaves are trifoliate (rarely, they have four or more leaflets; the more leaflets the leaf has, the rarer it is; see four-leaf clover), with stipules adnate to the leaf-stalk, and heads or dense spikes of small red, purple, white, or yellow flowers; the small, few-seeded pods are enclosed in the calyx. Other closely related genera often called clovers include Melilotus (sweet clover) and Medicago (alfalfa or Calvary clover).
Cultivation
Several species of clover are extensively cultivated as fodder plants. The most widely cultivated clovers are white clover, Trifolium repens, and red clover, Trifolium pratense. Clover, either sown alone or in mixture with ryegrass, has for a long time formed a staple crop for silaging, for several reasons: it grows freely, shooting up again after repeated mowings; it produces an abundant crop; it is palatable to and nutritious for livestock; it fixes nitrogen, reducing the need for synthetic fertilizers; it grows in a great range of soils and climates; and it is appropriate for either pasturage or green composting.
In many areas, particularly on acidic soil, clover is short-lived because of a combination of insect pests, diseases and nutrient balance; this is known as "clover sickness". When crop rotations are managed so that clover does not recur at intervals shorter than eight years, it grows with much of its pristine vigor.
Clovers are most efficiently pollinated by bumblebees, which have declined as a result of agricultural intensification. Honeybees can also pollinate clover, and beekeepers are often in heavy demand from farmers with clover pastures. Farmers reap the benefits of increased reseeding that occurs with increased bee activity, which means that future clover yields remain abundant. Beekeepers benefit from the clover bloom, as clover is one of the main nectar sources for honeybees.
Trifolium repens, white or Dutch clover, is a perennial abundant in meadows and good pastures. The flowers are white or pinkish, becoming brown and deflexed as the corolla fades. Trifolium hybridum, alsike or Swedish clover, is a perennial which was introduced early in the 19th century and has now become naturalized in Britain. The flowers are white or rosy, and resemble those of Trifolium repens. Trifolium medium, meadow or zigzag clover, a perennial with straggling flexuous stems and rose-purple flowers, has potential for interbreeding with T. pratense to produce perennial crop plants.
Other species are: Trifolium arvense, hare's-foot trefoil; found in fields and dry pastures, a soft hairy plant with minute white or pale pink flowers and feathery sepals; Trifolium fragiferum, strawberry clover, with globose, rose-purple heads and swollen calyxes; Trifolium campestre, hop trefoil, on dry pastures and roadsides, the heads of pale yellow flowers suggesting miniature hops; and the somewhat similar Trifolium dubium, common in pastures and roadsides, with smaller heads and small yellow flowers turning dark brown.
Uses
Clover is foraged by wildlife, including bears, game animals, and birds. Native Americans ate the plants raw and cooked, drying and smoking the roots. The seeds from the blossoms were used to make bread. It is also possible to make tea from the blossoms.
Symbolism
Shamrock, the traditional Irish symbol, which according to legend was coined by Saint Patrick for the Holy Trinity, is commonly associated with clover, although alternatively sometimes with the various species within the genus Oxalis, which are also trifoliate.
Clovers occasionally have four leaflets, instead of the usual three. These four-leaf clovers, like other rarities, are considered lucky. Clovers can also have five, six, or more leaflets, but these are rarer still. The clover's outer leaf structure varies in physical orientation. The record for most leaflets is 56, set on 10 May 2009. This beat the "21-leaf clover", a record set in June 2008 by the same discoverer, who had also held the prior Guinness World Record of 18.
A common idiom is "to be (or to live) in clover", meaning to live a carefree life of ease, comfort, or prosperity.
A cloverleaf interchange is named for the resemblance to the leaflets of a (four-leaf) clover when viewed from the air.
Phylogeny
The first extensive classification of Trifolium was done by Zohary and Heller in 1984. They divided the genus into eight sections: Lotoidea, Paramesus, Mistyllus, Vesicamridula, Chronosemium, Trifolium, Trichoecephalum, and Involucrarium, with Lotoidea placed most basally. Within this classification system, Trifolium repens falls within section Lotoidea, the largest and least heterogeneous section. Lotoidea contains species from America, Africa, and Eurasia, considered a clade because of their inflorescence shape, floral structure, and legume that protrudes from the calyx. However, these traits are not unique to the section, and are shared with many other species in other sections. Zohary and Heller argued that the presence of these traits in other sections proved the basal position of Lotoidea, because they were ancestral. Aside from considering this section basal, they did not propose relationships between other sections.
Since then, molecular data has both questioned and confirmed the proposed phylogeny from Zohary and Heller. A genus-wide molecular study has since proposed a new classification system, made up of two subgenera, Chronosemium and Trifolium. This recent reclassification further divides subgenus Trifolium into eight sections. The molecular data supports the monophyletic nature of three sections proposed by Zohary and Heller (Tripholium, Paramesus, and Trichoecepalum), but not of Lotoidea (members of this section have since been reclassified into five other sections). Other molecular studies, although smaller, support the need to reorganize Lotoidea.
Species
291 species of Trifolium are currently accepted:
Trifolium absconditum
Trifolium acaule Steud. ex A.Rich.
Trifolium affine C.Presl
Trifolium acutiflorum
Trifolium × adulterinum
Trifolium affine
Trifolium africanum Ser.
Trifolium aintabense Boiss. & Hausskn.
Trifolium albopurpureum Torr. & A. Gray – rancheria clover
Trifolium alexandrinum L. – Egyptian clover, berseem clover
Trifolium alpestre L.
Trifolium alpinum L. – alpine clover
Trifolium alsadami
Trifolium amabile Kunth
Trifolium ambiguum M. Bieb.
Trifolium amoenum Greene – showy Indian clover
Trifolium amphianthum
Trifolium andersonii A. Gray – Anderson's clover or fiveleaf clover
Trifolium andinum Nutt. – Intermountain clover
Trifolium andricum Lassen
Trifolium angulatum Waldst. & Kit.
Trifolium angustifolium L.
Trifolium ankaratrense
Trifolium apertum Bobrov
Trifolium appendiculatum
Trifolium argutum Banks & Sol.
Trifolium arvense L. – hare's-foot clover
Trifolium attenuatum Greene
Trifolium aureum Pollich – large hop trefoil
Trifolium baccarinii Chiov.
Trifolium badium Schreb.
Trifolium barbigerum Torr. – bearded clover
Trifolium barbulatum
Trifolium barnebyi (Isely) Dorn & Lichvar
Trifolium batmanicum Katzn.
Trifolium beckwithii W.H.Brewer ex S.Watson – Beckwith's clover
Trifolium bejariense Moric.
Trifolium × bertrandii
Trifolium berytheum Boiss. & C.I.Blanche
Trifolium biebersteinii
Trifolium bifidum A.Gray – notchleaf clover
Trifolium bilineatum Fresen.
Trifolium billardierei Spreng.
Trifolium bithynicum
Trifolium bivonae Guss.
Trifolium blancheanum Boiss.
Trifolium bobrovii
Trifolium bocconei Savi
Trifolium boissieri Guss.
Trifolium bolanderi A.Gray
Trifolium bordsilovskyi
Trifolium brandegeei S.Watson
Trifolium breweri S. Watson – forest clover
Trifolium brutium Ten.
Trifolium buckwestiorum Isely – Santa Cruz clover
Trifolium bullatum Boiss. & Hausskn.
Trifolium burchellianum Ser.
Trifolium calcaricum J.L.Collins & Wieboldt
Trifolium calocephalum Fresen.
Trifolium campestre Schreb. – hop trefoil
Trifolium canescens Willd.
Trifolium carolinianum Michx.
Trifolium caudatum Boiss.
Trifolium cernuum Brot.
Trifolium cheranganiense J.B.Gillett
Trifolium cherleri L.
Trifolium chilaloense Thulin
Trifolium chilense Hook. & Arn.
Trifolium chlorotrichum Boiss. & Balansa
Trifolium ciliolatum Benth. – foothill clover
Trifolium circumdatum Kunze
Trifolium clusii Godr.
Trifolium clypeatum L.
Trifolium congestum Guss.
Trifolium constantinopolitanum Ser.
Trifolium cryptopodium Steud. ex A. Rich.
Trifolium cyathiferum Lindl. – cup clover
Trifolium dalmaticum Vis.
Trifolium dasyphyllum Torr. & A.Gray
Trifolium dasyurum C.Presl
Trifolium davisii E.Hossain
Trifolium decorum Chiov.
Trifolium dedeckerae
Trifolium depauperatum Desv. – cowbag clover, balloon sack clover, or poverty clover
Trifolium dichotomum Hook. & Arn.
Trifolium dichroanthoides Rech.f.
Trifolium dichroanthum Boiss.
Trifolium diffusum Ehrh.
Trifolium dolopium Heldr. & Hochst. ex Gibelli & Belli
Trifolium douglasii House
Trifolium dubium Sibth. – lesser hop trefoil
Trifolium echinatum M.Bieb.
Trifolium egrissicum
Trifolium elgonense J.B.Gillett
Trifolium elizabethiae
Trifolium eriocephalum Nutt. – woollyhead clover
Trifolium eriosphaerum Boiss.
Trifolium erubescens Fenzl
Trifolium euxinum Zohary
Trifolium eximium Stephan ex Ser.
Trifolium farayense
Trifolium fergan-karaeri
Trifolium fontanum
Trifolium fragiferum L. – strawberry clover
Trifolium friscanum (S.L.Welsh) S.L.Welsh
Trifolium fucatum Lindl. – bull clover or sour clover
Trifolium gemellum Pourr. ex Willd.
Trifolium gillettianum Jacq.-Fél.
Trifolium glanduliferum Boiss.
Trifolium globosum L.
Trifolium glomeratum L. – clustered clover or bush clover
Trifolium gordeievii (Kom.) Z.Wei
Trifolium gracilentum Torr. & A.Gray – pinpoint clover
Trifolium grandiflorum Schreb.
Trifolium gymnocarpon Nutt. – hollyleaf clover
Trifolium hatschbachii
Trifolium haussknechtii Boiss.
Trifolium haydenii Porter
Trifolium heldreichianum (Gibelli & Belli) Hausskn.
Trifolium hickeyi
Trifolium hirtum All. – rose clover
Trifolium howellii S.Watson – canyon clover or Howell's clover
Trifolium humile
Trifolium hybridum L. – Alsike clover
Trifolium hydrophilum
Trifolium incarnatum L. – crimson clover
Trifolium infamia-ponertii
Trifolium israeliticum Zohary & Katzn.
Trifolium isthmocarpum Brot.
Trifolium jokerstii Vincent & Rand.Morgan
Trifolium juliani Batt.
Trifolium kentuckiense Chapel & Vincent
Trifolium kingii S.Watson
Trifolium lanceolatum (J.B.Gillett) J.B.Gillett
Trifolium lappaceum L.
Trifolium latifolium (Hook.) Greene
Trifolium latinum Sebast.
Trifolium leibergii A.Nelson & J.F.Macbr. – Leiberg's clover
Trifolium lemmonii S.Watson – Lemmon's clover
Trifolium leucanthum M.Bieb.
Trifolium ligusticum Balb. ex Loisel.
Trifolium longidentatum Nábelek
Trifolium longipes Nutt. – longstalk clover
Trifolium lucanicum Gasp.
Trifolium lugardii Bullock
Trifolium lupinaster L.
Trifolium macilentum Greene
Trifolium macraei Hook. & Arn. – Chilean clover, double-head clover, or MacRae's clover
Trifolium macrocephalum (Pursh) Poir. – largehead clover
Trifolium masaiense J.B.Gillett
Trifolium mattirolianum Chiov.
Trifolium mazanderanicum Rech.f.
Trifolium medium L. – zigzag clover
Trifolium meduseum C.I.Blanche ex Boiss.
Trifolium meironense Zohary & Lerner
Trifolium mesogitanum
Trifolium michaelis
Trifolium michelianum Savi
Trifolium micranthum Viv.
Trifolium microcephalum Pursh – smallhead clover
Trifolium microdon Hook. & Arn. – thimble clover
Trifolium miegeanum Maire
Trifolium minutissimum
Trifolium modestum
Trifolium monanthum A.Gray – mountain carpet clover
Trifolium montanum L.
Trifolium multinerve A. Rich.
Trifolium multistriatum W.D.J.Koch
Trifolium mutabile Port.
Trifolium nanum Torr.
Trifolium nerimaniae M.Keskin
Trifolium × neyrautii
Trifolium nigrescens Viv.
Trifolium noricum Wulfen
Trifolium obscurum Savi
Trifolium obtusiflorum Hook. – clammy clover
Trifolium occidentale Coombe
Trifolium ochroleucon Huds. - sulphur clover
Trifolium oliganthum Steud. – fewflower clover
Trifolium olivaceum
Trifolium orbelicum
Trifolium ornithopodioides L.
Trifolium owyheense Gilkey
Trifolium pachycalyx Zohary
Trifolium palaestinum Boiss.
Trifolium pallescens Schreb.
Trifolium pallidum Waldst. & Kit.
Trifolium palmeri
Trifolium pamphylicum
Trifolium pannonicum Jacq. – Hungarian clover
Trifolium parnassi Boiss. & Spruner
Trifolium parryi A.Gray
Trifolium patens Schreb.
Trifolium patulum Tausch
Trifolium pauciflorum d'Urv.
Trifolium × permixtum
Trifolium peruvianum Vogel
Trifolium philistaeum Zohary
Trifolium phitosianum N.Böhling, Greuter & Raus
Trifolium phleoides Pourr. ex Willd.
Trifolium physanthum Hook. & Arn.
Trifolium physodes Steven ex M. Bieb.
Trifolium pichisermollii J.B.Gillett
Trifolium pignantii Fauché. & Chaub.
Trifolium pilczii Adamović
Trifolium pilulare Boiss.
Trifolium piorkowskii Rand.Morgan & A.L.Barber
Trifolium plebeium Boiss.
Trifolium plumosum Douglas ex Hook.
Trifolium polymorphum Poir.
Trifolium polyodon Greene
Trifolium polyphyllum C.A.Mey.
Trifolium polystachyum Fresen.
Trifolium praetermissum Greuter, Pleger & Raus.
Trifolium pratense L. – red clover
Trifolium productum
Trifolium prophetarum M. Hossain
Trifolium pseudomedium
Trifolium pseudostriatum Baker f.
Trifolium pulchellum
Trifolium purpureum Loisel.
Trifolium purseglovei J. B. Gillett
Trifolium quartinianum A. Rich.
Trifolium radicosum Boiss. & Hohen.
Trifolium rechingeri
Trifolium reflexum L. – buffalo clover
Trifolium repens L. – shamrock (white clover)
Trifolium resupinatum L. – Persian clover, shaftal
Trifolium retusum L.
Trifolium × retyezaticum
Trifolium rhizomatosum
Trifolium rhombeum
Trifolium riograndense Burkart
Trifolium rollinsii
Trifolium roussaeanum Boiss.
Trifolium rubens L.
Trifolium rueppellianum Fresen.
Trifolium salmoneum Mouterde
Trifolium sannineum
Trifolium sarosiense
Trifolium saxatile All.
Trifolium scabrum L.
Trifolium schimperi (Hochst.) A.Rich.
Trifolium schneideri
Trifolium × schwarzii
Trifolium scutatum Boiss.
Trifolium sebastiani Savi
Trifolium semipilosum Fresen.
Trifolium setiferum Boiss.
Trifolium simense Fresen.
Trifolium sintenisii Freyn
Trifolium siskiyouense J.M.Gillett
Trifolium somalense Taub. ex Harms
Trifolium sonorense
Trifolium spadiceum L.
Trifolium spananthum Thulin
Trifolium spumosum L.
Trifolium squamosum (or maritimum) L. – sea clover
Trifolium squarrosum L.
Trifolium stellatum L.
Trifolium steudneri Schweinf.
Trifolium stipulaceum Thunb.
Trifolium stoloniferum Muhl. ex A. Eaton – running buffalo clover
Trifolium stolzii Harms
Trifolium striatum L. – knotted clover
Trifolium strictum L.
Trifolium subterraneum L. – subterranean clover
Trifolium suffocatum L.
Trifolium sylvaticum Gérard
Trifolium tembense Fresen.
Trifolium tenuifolium
Trifolium thalii Vill.
Trifolium thompsonii C.V.Morton – Thompson's clover
Trifolium tomentosum L.
Trifolium × traplii
Trifolium triaristatum Bertero ex Colla
Trifolium trichocalyx A.Heller – Monterey clover
Trifolium trichocephalum M. Bieb.
Trifolium trichopterum Pančić
Trifolium tumens Steven ex M.Bieb.
Trifolium ukingense Harms
Trifolium uniflorum L.
Trifolium usambarense Taub.
Trifolium variegatum Nutt. – whitetip clover
Trifolium vavilovii Eig
Trifolium velebiticum Degen
Trifolium velenovskyi Vandas
Trifolium vernum Phil.
Trifolium vesiculosum Savi
Trifolium vestitum D.Heller & Zohary
Trifolium virginicum Small
Trifolium wentzelianum Harms
Trifolium wettsteinii Dörfl. & Hayek
Trifolium wigginsii J. M. Gillett
Trifolium willdenovii Spreng. − tomcat clover
Trifolium wormskioldii Lehm. – cow clover
Trifolium xanthinum
See also
Clover honey
Cloverleaf quasar
Green manure
References
External links
Quattrofolium
Edibility of clover: Edible parts and visual identification of wild clover.
Nitrogen fixation
Forages
Garden plants
Groundcovers
Nitrogen-fixing crops
Taxa named by Carl Linnaeus